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S Wellek

Publications and source records attributed to S Wellek.

49 records · Page 3Linked to original sources
PubMed1991

Hydrochlorothiazide and verapamil in the treatment of hypertension. The Verapamil Versus Diuretic (VERDI) Trial Research Group.

The efficacy and tolerability of hydrochlorothiazide, sustained-release verapamil, and their combination was compared in patients with mild to moderate hypertension. The design was a multicenter, randomized, double-blind clinical trial with a single-blind placebo baseline period of 2 weeks. Three hundred sixty-nine patients with a diastolic blood pressure of 95-120 mm Hg were included. Treatment consisted of 12.5 mg of hydrochlorothiazide once daily, then 25 mg once daily, and finally 25 mg twice daily; the other group received verapamil at a dose of 120 mg once daily, then 240 mg once daily, and finally 240 mg twice daily. Patients not achieving target blood pressure (less than 90 mm Hg diastolic) were given the combination of hydrochlorothiazide and verapamil, that is, 25 and 240 mg once daily and twice daily. During all time points during the study patients receiving verapamil achieved target blood pressure more often than patients receiving hydrochlorothiazide (after 8 weeks, 57.7 and 42.7%; after 24 weeks, 46.8 and 26.4%; and after 48 weeks, 44.8 and 24.7%, respectively). Adding verapamil to hydrochlorothiazide was more effective in lowering blood pressure than adding hydrochlorothiazide to verapamil. The number of treatment withdrawals was essentially the same with the two drugs. Therefore, in the doses currently used in antihypertensive treatment, verapamil was more effective than hydrochlorothiazide as a single agent and in combination in mild to moderate hypertension.

Adult↗
PubMed1991

Elements of significance testing with equivalence problems.

The paper outlines an approach to the general methodological problem of equivalence assessment which is based on the classical theory of testing statistical hypotheses. Within this frame of reference it is natural to search for decision rules satisfying the same criteria of optimality which are customarily applied in deriving solutions to one- and two-sided testing problems. For three standard situations very frequently encountered in medical applications of statistics, a concise account of such an optimal test for equivalence is presented. It is pointed out that tests based on the well-known principle of confidence interval inclusion are valid in the sense of guaranteeing the prespecified level of significance, but tend to have an unnecessarily low efficiency.

Confidence Intervals↗
PubMed1990

Hemodynamics during PEEP ventilation in patients with severe left ventricular failure studied by transesophageal echocardiography.

The effects of mechanical ventilation with PEEP were investigated in five patients with normal cardiopulmonary function (group A) and in 11 patients with severe left ventricular failure (group B). Cross-sectional area of the right and left atrium (RA/LA), left ventricle (LV), and right ventricle (RV) was determined at EDA/ESA using transesophageal echocardiography. Hemodynamic parameters and transesophageal pressure were measured simultaneously at PEEP levels 0, 4, 8, 12, and 16 cm H2O. End-diastolic area of the right atrium decreased significantly in both groups. The RA pressure increased, while transmural pressure remained unaltered. The CI decreased in both groups. The decrease in cardiac output by PEEP ventilation was related to the decrease in RV filling volume by external compression. In patients with congestive heart failure, PEEP ventilation with 8 to 10 cm H2O did not worsen LV function.

Adult↗
PubMed1990

Reference standards for software evaluation.

The field of automated ECG analysis was one of the earliest topics in Medical Informatics and may be regarded as a model both for computer-assisted medical diagnosis and for evaluating medical diagnostic programs. The CSE project has set reference standards of two kinds: In a broad sense, a standard how to perform a comprehensive evaluation study, in a narrow sense, standards as specific references for evaluating computer ECG programs. The evaluation methodology used within the CSE project is described as a basis for presentation of results which are published elsewhere in this issue.

Diagnosis, Computer-Assisted↗
PubMed1989

Verapamil versus hydrochlorothiazide in the treatment of hypertension: results of long term double blind comparative trial. Verapamil versus Diuretic (VERDI) Trial Research Group.

OBJECTIVE: To compare the efficacy and tolerability of hydrochlorothiazide, sustained release verapamil, and their combination in patients with mild to moderate hypertension. DESIGN: Randomised multicentre trial of 48 weeks' duration with a double blind comparison of hydrochlorothiazide and verapamil followed by an open trial of combined treatment for patients not achieving the target diastolic blood pressure (less than 90 mm Hg) during treatment with a single drug. SETTING: Outpatient departments in 10 clinics and 10 private practices of general practitioners or internists. PATIENTS: 369 Hypertensive patients with a diastolic blood pressure of 95-120 mm Hg during a placebo run in period of two weeks. INTERVENTIONS: Initial treatment consisted of 12.5 mg hydrochlorothiazide (n = 187) or 120 mg sustained release verapamil (n = 182) once daily (regimen I). If the target diastolic blood pressure of less than 90 mm Hg was not achieved within four weeks doses were increased to 25 mg hydrochlorothiazide or 240 mg verapamil once (regimen II) and twice daily (regimen III). Patients not achieving target blood pressure were given the combination of hydrochlorothiazide and verapamil--that is, 25 and 240 mg once (regimen IV) and twice daily (regimen V). MAIN OUTCOME MEASURE: Blood pressure determined with a device permitting automatic repeated measurements with printouts. RESULTS: After eight weeks of treatment with a single drug 76 out of 178 (43%) and 101 out of 175 (58%) patients achieved the target blood pressure with hydrochlorothiazide and verapamil, respectively. During follow up until 48 weeks patients treated with verapamil reached the target blood pressure more often and at lower doses and were less likely to switch to combination treatment than patients randomised to hydrochlorothiazide treatment. Adding verapamil to hydrochlorothiazide was more effective than the addition of hydrochlorothiazide to verapamil. At the end of the study 42 out of 169 (25%) and 73 out of 163 (45%) patients initially randomised to hydrochlorothiazide and verapamil, respectively, were at target blood pressure without combination treatment. After adding verapamil to hydrochlorothiazide or hydrochlorothiazide to verapamil an additional 58 (34%) and 29 (18%) patients reached the target blood pressure, respectively. Altogether 92 out of 332 (28%) patients failed to achieve target blood pressure with regimen V. There were four, 10, seven, and seven withdrawals due to possible adverse effects to treatment with hydrochlorothiazide, verapamil, combining verapamil with hydrochlorothiazide, and combining hydrochlorothiazide with verapamil, respectively. CONCLUSIONS: In doses currently used in antihypertensive treatment verapamil was more effective than hydrochlorothiazide as a single agent and in combination in mild to moderate hypertension, whereas withdrawal rates caused by side effects possibly related to treatment were similar.

Adult↗
PubMed1981

[On the statistical analysis of long-term tests for carcinogenesis by means of the random censorship model (author's transl)].

In Section 1 we discuss the fundamental point that the overall tumour incidence rates observed in long-term tests for carcinogenesis typically are biased by differences in intercurrent mortality. In view of some more recent results from theoretical statistics an application of the random censorship model provides an especially powerful approach to getting along with this difficulty. The main assumptions making up the random censorship model as to be applied to the special case of long-term carcinogenesis assay data are carefully described. A consistent and unbiased method for calculating tumour incidence rates corrected for tumour independent intercurrent mortality from the data of an experiment which satisfies the aforementioned assumptions is provided by the Kaplan-Meier technique. Full computational details of the Kaplan-Meier procedure are presented in Section 2. Section 3 is concerned with significance tests for judging dose effects on standardized tumour induction rates. The stepwise procedure recently developed by Holm is adapted to the multiple comparison of several single doses of a possibly carcinogenic compound to the same control. A significance test specifically designed for the assessment of an increasing dose dependent trend is due to Cox and Tarone. Formulas enabling to an easy performance of the Cox-Tarone test are also explicitly written down. In Section 4 we show how to take advantage of Cox's "proportional hazards model" in establishing approximate dose-response relationships.--In each case the general description of the computational procedure is illustrated by an elaborate real data example from a study (published in the same issue of this journal) on the carcinogenicity of ethylene oxide and 1,2-propylene oxide after subcutaneous administration in mice.

Animals↗
PubMed1979

[Acute leukemia in multiple myeloma: case histories, a review of the literature and assessment of the incidence].

The results of a follow-up study of 112 patients with multiple myeloma are presented. Three of these patients developed acute leukaemia during the respective period of clinical observation (maximum: 11 years)--one case of acute myeloblastic leukaemia, myelomonocytic leukaemia and erythroleukaemia, respectively. For estimating the incidence of acute leukaemia in the presence of multiple myeloma an extended life table method was applied. On the basis of our data this method gave a probability of 5.9% for a patient to develop acute leukaemia at any time after the diagnosis of multiple myeloma. In a statistical discussion this result is considered to confirm the assumption of a highly increased AL-risk in patients with multiple myeloma. In a survey of the literature some important data of 100 cases with the association acute leukaemia--multiple myeloma are reported.

Acute Disease↗
PubMedDate not supplied

[Medulloblastoma therapy studies MBL 80 and MED 84 of the Society of Pediatric Oncology and the Société Internationale d'Oncologie Pédiatrique (SIOP)].

In both trials the principle of "sandwich" chemotherapy (administered between surgery and postoperative irradiation) is studied in medulloblastoma. GPO-MBL 80 was essentially a one-arm trial; results after a mean observation period of 3 years show an expected event-free survival rate of 46% at 6 years. "Maintenance" chemotherapy with CCNU and vincristine did not further improve the results. Preliminary results of the joint, prospective, randomised forearm SIOP-GPO trial MED 84 are presented. It is apparently too early to answer any of the two main questions asked by this trial: a) is "sandwich" chemotherapy (as administered) of any value? b) can radiotherapy doses to the supratentorial area and to the spine be moderately reduced in so-called "low risk" patients without compromising long-term results? Thus far, we cannot observe any prognostic influence of the "classical" risk factors as established by other studies.

Adolescent↗
PubMedDate not supplied

[Significance of pathological alpha-1-fetoprotein levels in the framework of prenatal diagnosis].

Merkatz (1984) showed that in 68% of live birth with Down Syndrome maternal age was 34 years or less. It would be desirable to define a high risk collective of women younger then 35 years with the help of a screening test, which could further on lead to a prenatal diagnostics. Several studies showed that low maternal serum alpha-fetoprotein levels (SAFP) in pregnancy is associated with fetal chromosomal abnormalities. The results of a retrospective study at the Department of Obstetrics and Gynecology at University of Mainz showed that maternal SAFP-level does not accomplish the demand of a prenatal screening test, because only 17% of the Down Syndrome could be diagnosed by this parameter. In case of trisomy 13 and 18 SAFP-concentrations were normal or even increased, maybe on account of the combination with other malformations like neural-tube or abdominal-wall defects.

Adult↗